1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, for example, and in particular, relates to a stator construction for an alternator mounted to an automotive vehicle such as a passenger car or a truck.
2. Description of the Related Art
FIG. 15 is a perspective showing a stator of a conventional alternator. In the stator 208 of the conventional alternator, wind noise is reduced by smoothing surfaces having irregularities due to a number of bundles of coils by disposing a resin 202 so as to completely cover coil end portions which are portions of the coils which are exposed outside a stator core 15. That is to say, in the coil end portions, the coils, which generate heat, are cooled by a cooling air flow generated by a fan disposed on a rotor which is not shown, but by disposing the resin 202 and making the surfaces of the coil ends smooth, interference between the fan and the coils is decreased, reducing wind noise.
However, in the conventional alternator constructed in this manner, because the coil ends are completely covered by the resin 202, the environment becomes severe for the coil ends, which are heat-generating bodies, and this has a large deleterious effect on output from the alternator. Furthermore, in molding the resin 202, because a mold completely covering the coil end portions is prepared, for example, and softened resin is poured into the mold and hardened, workability has been poor.
If the alternator is a three-phase alternator, because three coil turn groups partially overlap in the coil end portions and are not aligned, it is difficult to distribute the resin 202 disposed on the coil end portions uniformly around the entire circumference, making the shape of the resin 202 biased in both an axial direction and a circumferential direction, causing cooling to become non-uniform and wind noise to worsen.
The present invention aims to solve the above problems and an object of the present invention is to provide an alternator which can improve cooling of a stator winding and reduce wind noise.
In order to achieve the above object, according to one aspect of the present invention, there is provided an alternator including: a rotor including:
claw-shaped magnetic poles fitted onto a rotating shaft; and
a cooling means disposed on the claw-shaped magnetic poles; and a stator including:
a stator core disposed facing the rotor, the stator core having a plurality of slots; and
a stator winding installed in the stator core, the stator being cooled by the cooling means; and a bracket for supporting the rotor and the stator, a passage for a cooling air flow generated by the cooling means being disposed inside the bracket, the stator winding including coil ends extending outwards from end surfaces of the stator core, and a shielding material being disposed so as to cover at least an inner circumferential surface of the coil ends.
Apertures may be formed in a main surface of the shielding material.
Protrusions and recesses may be formed on a surface of the shielding material.
The shielding material covering the coil ends may be secured by a second resin whose thermal conductivity is greater than a first resin disposed on the coil ends.
Return portions of the stator winding crossing over between slots separated at a predetermined pitch may be formed with a generally identical shape in a circumferential direction in at least one of the coil ends of the stator.
Spaces between circumferentially-adjacent return portions of the stator winding crossing over between slots separated at a predetermined pitch may be formed so as to be generally identical in at least one of the coil ends of the stator.
A cross-sectional shape of conductors of the stator winding within the slots may be a generally rectangular shape following a shape of the slots.
In addition, at least one of said coil ends may be disposed in close proximity to a downstream end of the cooling air flow generated by the cooling means.